SFTPD and chronic obstructive pulmonary disease: As pointed out by Watson et al. (23), partially due to leakage from the lung, elevated plasma levels of SP-D have been shown to correlate with the early phase of COPD exacerbations in AECOPD and indices of lung function, including FEV1 and the BODE (body mass index, airflow obstruction, dyspnea, exercise capacity) index in stable COPD (136, 137).